The present invention relates generally to laser systems, and more particularly, to an improved dual cavity multifunction laser system.
In typical single resonator lasers, it is difficult to produce the combination of short, low energy and long, high energy pulses from the same resonator. This is because high gain (high energy) systems typically produce short pulses and low gain (lower energy) systems typically produce longer pulses. It has been determined that by using two different length resonators with identical bounce paths through the slab, Brewster face losses and thermally induced birefringence can be minimized for both resonators. In addition, both resonators can share common optical components such as an electro-optical Q-switch, hold off polarizer, rear reflector, and compensating cylindrical len(s). These shared components do not have to be replicated for each resonator and thus reduce system cost and complexity.
A recent publication, xe2x80x9cDiode-pumped high-efficiency high-brightness Q-switched Nd:YAG slab laser,xe2x80x9d by E. Armandillo, et al., Opt. Lett., 22, 1168-1170 (1997), describes the performance of a contact cooled, diode-pumped slab laser using an unstable resonator with a Gaussian reflectivity output coupler. These authors do not disclose or suggest a resonator that uses a dual cavity, shared gain region resonator approach which allows the generation of two distinct pulse widths from the same gain medium, a polarization selection strategy to differentiate the two resonator paths, a variable diode-to-slab optical coupling system which allows variable diode pump light distribution within the slab, or super Gaussian reflectivity output couplers to tailor output laser beam transverse profiles for optimized nonlinear conversion of external converters (e.g., KTA, KTP (OPOs), frequency doubling crystals, etc.).
It would therefore be desirable to have a dual cavity multifunction laser system that improves upon conventional designs.
The present invention provides for a dual cavity multifunction laser comprising a diode-pumped, contact cooled, slab laser head that supports two different length unstable resonators. In its basic form, the dual cavity multifunction laser comprises a common rear reflector, an electro-optical Q-switch, a first gain medium, a halfwave plate, and a cavity switching polarizer. These components are common to both cavities. A short cavity is provided that outputs a high repetition rate, low pulse energy output beam that includes these basic components along with a short cavity super Gaussian output coupler that defines the length of the short cavity. A correcting cylindrical lens is employed that is specific to the short cavity. A long cavity is provided that outputs a low repetition rate, high pulse energy output beam and includes the basic components along with a long cavity super Gaussian output coupler that defines the length of the long cavity. The output of the long cavity may be coupled to an external amplifier gain medium by way of a halfwave plate and an optical isolator to produce the low repetition rate, high pulse energy output beam that may be used for designator purposes, for example.
The dual cavity multifunction laser produces short ( less than 8 ns), low energy 1 xcexcm pulses or long ( greater than 15 ns), higher energy 1 xcexcm pulses from the same laser head at different repetition rates, if desired. The utility of two distinct pulse widths, pulse energies, and repetition rates is that the output from each resonator can be separately optimized for different operating modes (e.g., target designation and target profiling). The unstable resonators use independently optimized super Gaussian output couplers to generate high quality beams for each of the high and low pulse energy modes. The resonators also share a common bounce path through the slab laser head to minimize intracavity losses and thermally induced birefringence for both resonators.
The dual cavity multifunction laser system produces, from a single laser system, both high energy, relatively long ( greater than 15 ns) pulses and low energy, short ( less than 8 ns) pulses, which is extremely difficult from a single resonator laser system. These distinct pulse widths, pulse energies, and repetition rates can be used to optimize separate functions, such as for target designation and target profiling.
Advantages of the dual cavity multifunction laser are that it has lower system costs (relative to two independent lasers) due to shared laser slab, pump diodes, diode coupling optics, the electro-optical Q-switch, hold off polarizer, rear reflector, and compensating cylindrical len(s). The present laser has the ability to produce varying pulse widths, pulse energies, repetition rates, and different high quality beam profiles from a single laser system. The present laser provides two distinct output beams for pumping separate nonlinear frequency conversion devices, if desired. The present laser also has a reduced parts count and complexity relative to two independent lasers.
The dual cavity, multifunction laser system may be used as a laser device for a multitude of multifunction laser applications that require mutifunctionality from a single laser system.